1. Field of the Invention
The invention pertains to improved textile finishes.
2. Description of the Prior Art
U.S. Pat. No. 3,211,805 discloses the preparation of mixtures of substantially fully methylolated melamine-ethylene urea-formaldehyde compositions characterized by high water solubility and excellent storage stability. However, these mixtures are not without deficiencies, particularly in the fact that they have 3-4% free formaldehyde content.
The presence of free formaldehyde in amounts of 3-4% based on the total weight of the product is undesirable since the amounts are sufficient to render the material commercially unattractive because of the noxious odors which are produced on heating textile materials treated therewith.
Stable mixtures of methylolated melamines, methylolated urea and glyoxal are disclosed by Sandler et al in Canadian Pat. No. 903,392. However, the Sandler disclosure does not relate to mixtures containing etherified melamine-formaldehyde resins. In particular this invention differs from the process of Sandler et al in that the composition of this invention is subjected to acidic conditions, the pH being as low as 2.5 preparation lower.
Frequently, prior art refers to the reaction products as being highly stable and infinitely soluble in water. In practice, it has been found that by adhering to the conditions described in such disclosures many infinitely water-soluble melamine resins can be so prepared, as for example, trimethyl trimethylol melamine, tetramethyl pentamethylol melamine, and the like. However, it has been my experience that when these teachings are applied to the preparation of mixtures containing a substantially fully etherified, substantially fully methylolated melamine, the resulting product does not possess the necessary degree of water solubility and stability for a good textile resin.
The reasons for the poor water solubility and stability of many prior art mixtures containing substantially fully etherified, substantially fully methylolated resins have been speculated upon in the art. A strong body of opinion supports the theory that these deficiencies are developed in the product when it is attempted to obtain full etherification because of the conditions employed.
In recent years the free formaldehyde content of aqueous solutions of methylol carbamates has been reduced by contacting the solution with a pyrollidone in the presence of caustic as disclosed in U.S. Pat. No. 3,749,751. However, the use of pyrollidone is expensive. Very often efforts to physically reduce the free formaldehyde content to an acceptable level, as by vacuum concentration to less than 3% based on total composition, impairs the solubility of the resin in water. Common methods of removing the excess formaldehyde such as by isolating the methylolated melamine are too costly.